My mistake, I meant car seal open the block valves, not relief valves. So, basically it sounds like even though the valve is fail open, you have to consider it getting closed and blocking the relief flow.
I am evaluating some exchangers to determine if we need a relief valve. The only case is fire. If we car seal open the relief valves, the exchangers can relieve back to the tower. However, there is a fail open control valve in the path. My boss says you can't relieve through a control valve...
